Method and apparatus for mounting pumps within a suction vessel

ABSTRACT

A pressure vessel and submerged electric motor pump system may include a pressure vessel and at least two motor-pump assemblies located within the pressure vessel. Each of the at least two motor-pump assemblies may include a submersible electric motor and a submersible pump in operable communication with the submersible electrical motor. The submersible pump may be configured to pump fluid from within the pressure vessel to without the pressure vessel. A method for pumping a fluid from a pressure vessel may include supplying a fluid to a pressure vessel, pumping the fluid with two or more submersible electric motor pumps located within the pressure vessel and discharging a pumped fluid from the pressure vessel.

BACKGROUND

This invention relates generally to submerged electric motor pumps, and, more particularly, this invention relates to submerged electric motor pumps having a unique pressure vessel design.

Submerged electric motor pumps mounted in their own suction or pressure vessels have found use in a variety of industries. Some uses include, but are not limited to, the pumping of cryogenic fluids such as liquid natural gas, and also corrosive and/or hazardous liquids. A typical configuration of a pressure vessel mounted submerged electric motor pump is one that has a centrifugal pump and motor assembly installed in a pressure vessel, with the pressure vessel filled with the liquid being pumped. The vessel may be any material but typically is stainless steel, and designed and fabricated in accordance with the appropriate pressure vessel code, Section VIII of the ASME Pressure Vessel Code in the USA, for instance.

FIG. 1 shows a known pressure vessel and submerged electric motor pump system 10. A pressure vessel 14 has contained within it a centrifugal pump 18 (either single or any number of stages) and an electric motor 22. Each vessel is equipped with nozzles 26 or fittings for suction, discharge 30, vent 34, drain 38 and electrical connection 42. There additionally may be one or more instrumentation connections 46.

It is common to install two or more pressure vessel mounted submerged electric motor pump systems in order to increase the total pumping capacity and/or to have spare capacity in case one of the pressure vessel and submerged electric motor pump systems should malfunction. Such systems are usually installed in parallel with each other. The parallel systems are fed from a common suction source with individual piping (and isolation valves) to the suction nozzle of each of the pumps. Similarly each system is fitted with individual discharge 30, vent line 34, drain line 38 and electrical connections 42 and may also each have an instrumentation connection 46. Of course all of the fluid lines will have the appropriate isolation and non-return valves. Further, the individual suction, drain and vent lines may be routed to a separate suction and phase separation vessel usually mounted at a higher elevation. In addition, each of the individual pump suction vessels requires its own mounting structure. The footprint of such a parallel configuration is very large and requires much space. This space may be difficult to come by in certain applications, such as applications on board ships and/or off shore platforms, or floating storage and regasification vessels (FSRV). Additionally, the separate piping, lines, and valves coupled to each of the pressure vessel and submerged electric motor pump systems increase cost and make the overall system very complex, and therefore more difficult and expensive to install and maintain.

BRIEF SUMMARY

Disclosed herein are embodiments relating to a pressure vessel and submerged electric motor pump system including a pressure vessel, at least two motor-pump assemblies located within the pressure vessel, each of the at least two motor-pump assemblies including a submersible electric motor, and a submersible pump in operable communication with the submersible electrical motor, and the submersible pump is configured to pump fluid from within the pressure vessel to without the pressure vessel.

Also disclosed herein are embodiments relating to a system including a pressure vessel, a single suction and phase separation vessel in operable communication with the pressure vessel, at least two motor-pump assemblies located within the pressure vessel, each of the at least two motor-pump assemblies having a submersible electric motor, and a submersible pump coupled to the submersible electrical motor, wherein the submersible pump is configured to pump fluid from within the pressure vessel to without the pressure vessel.

Also disclosed herein are embodiments relating to a method for pumping a fluid from a pressure vessel, the method including supplying a fluid to a pressure vessel, pumping the fluid with two or more submersible electric motor pumps located within the pressure vessel, and discharging a pumped fluid from the pressure vessel.

Also disclosed herein are embodiments relating to a method for pumping a fluid from a pressure vessel, the method including supplying power to two or more submersible electric motors located within the pressure vessel, rotating a rotor located within each of the two or more submersible electric motors, rotating two or more pump shafts each of which are within a separate pump and each of which are in operable communication with each of the rotors. The method further includes pumping a fluid within the pressure vessel with each of the pumps and discharging a pumped fluid from the pressure vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the figures, which are exemplary embodiments and wherein like elements are numbered alike:

FIG. 1 is a sectional view of a known single pressure vessel mounted submerged electric motor pump system;

FIG. 2 is a front view of the disclosed pressure vessel and submerged electric motor pumps system;

FIG. 3 is a side view of the system shown in FIG. 2;

FIG. 4 is a side view of a system with a foot valve located at the suction end of the pump; and,

FIG. 5 is a front view of the system shown in FIG. 4.

DETAILED DESCRIPTION

The disclosed pressure vessel mounted submerged electric motor pump system comprises two or more pumps within one pressure vessel. No other known pressure vessel pump system for cryogenic liquefied gas has two or more pumps within one pressure vessel. Advantages of having two or more pumps within one pressure vessel is that suction piping and vent piping are simplified, and cost and space required are reduced. Submerged electric motor pump systems with two or more pumps within one pressure vessel will have a smaller footprint than two or more pressure vessel and submerged electric motor pump systems. This smaller footprint is especially advantageous where space is at a premium, such as, but not limited to, offshore platforms, and shipboard installations. Additionally, since there is only one pressure vessel, as opposed to two or more pressure vessels, there only needs to be one set of pressure vessel piping, as opposed to two or more sets of pressure vessel suction and vent piping, thus making for less complex and less costly installation.

FIGS. 2 and 3 show two views of one embodiment of the disclosed pressure vessel and submerged electric motor pump system 50. The pressure vessel 54 has a plurality of support columns 58, 62, 66, 72 each of which is configured to support a submersible electric motor pump.

FIG. 3 shows a cut-away view through support column 58 enabling one to see the motor 108 and the pump 112. In this view, it can be seen that the support column 58 is fastened to the pressure vessel 54 as an extension of the pressure vessel 54. Thus it is clear that as an extension of the pressure vessel 54, the support column 58 is able to withstand the same internal fluid pressures as the remainder of the pressure vessel 54. A head plate 116 may be attached to an end of the support column 58. The head plate 116 provides access to the interior of the pressure vessel 54. The motor 108 comprises a sealed housing 110 and an electric motor (not seen in this view) with a rotor (not seen in this view) located within the housing 110. The motor housing 110 may be attached and supported by the head plate 116. The pump 112 comprises a housing 114, a pump shaft (not seen in this view), and impellers (not seen in this view). The motor housing 108 may be attached to a head plate 116 of the support column 58. The pump housing 114 may be attached to the motor housing 110. Within the housings 110,114, the pump shaft is normally coupled to the rotor of the electric motor. The coupling may be a flexible or rigid coupling, but it is necessary to choose a coupling able to withstand the particular conditions within the pressure vessel, which may be extremely cold if cryogenic fluid is being pumped or highly corrosive if certain corrosive fluids are being pumped. The interior of the pressure vessel may include support struts 120 or other means attached to the pump housing 114 in order to provide lateral support to the pump 112. The methods of attachment for each of the above structures may include bolting the structures together, however, other methods may be used, including, but not limited to: welding, using threaded fittings, using mating pieces, such as, but not limited to: socket and post. The pressure vessel 54 may have support webs 124 to provide support and stabilization to the support column 58. Although support webs 124 are shown, any of a number of known support structures may be used.

Although only one motor-pump pair's configuration was described above with respect to FIG. 3, the other motor pump pairs within support columns 62, 66, 72 may be configured in the same or similar way. However, there may be situations where the motor-pump pairs for one or more of the support columns may be configured differently than the other pairs, for instance if a different sized pump or motor were installed.

The pump 112 shown in FIG. 3 is a vertical pump, however, the pressure vessel and submerged electric motor pump system 50 may be configured to house horizontal pumps, or pumps positioned at some orientation other than vertical or horizontal, depending on the user's requirements. Often times, floor space is a limiting factor and a vertically oriented pump system typically has a smaller footprint than a horizontally oriented pump system. It should be noted that the pump 112 may be any of a number of types of pumps, including, but not limited to: centrifugal pump, axial flow pumps, screw pumps, reciprocating pumps, positive displacement pumps and jet pumps.

Referring back to FIG. 2, the system may have four support columns 58, 62, 66, 72. It should be clear however, that other embodiments of the disclosed system may have as few as two centrifugal pumps and up to “N” centrifugal pumps, where N is a positive integer. The embodiment shown has two suction nozzles 76, however other embodiments may have as few as one suction nozzle, or three or more suction nozzles. The suction nozzles 76 may be coupled to an external fluid supply, thereby providing fluid to the interior of the pressure vessel 54, and ultimately to the inlet of the pumps located within the pressure vessel 54. The pressure vessel 54 may include one drain line 80 and at least one pressure vessel vent line 84, although the embodiment shown has two pressure vessel vent lines 84. The drain line 80 is coupleable to drain piping located without the pressure vessel 54. Because there is only one pressure vessel 54, there only needs to be one set of suction, drain and vent lines routed to a separate suction and phase separation vessel which would usually be mounted at a higher elevation. The two or more pressure vessels can also be configured to function as a phase separator which would eliminate the need for a separate suction and phase separation vessel. Also, since there is only one pressure vessel 54, only one mounting structure is necessary for the disclosed pressure vessel and submerged electric motor pump system 50.

Still referring to FIG. 2, each of the support columns 58, 62, 66, 72 may have a discharge line 88, and a vent line 92 extending therefrom which provides a means for fluid communication from within the pressure vessel to without (that is, to the exterior of) the pressure vessel. The discharge line 88 may be coupleable to piping located outside the pressure vessel 54. The piping located without the pressure vessel can transport the pumped fluid to some location. The vent line 92 may also be configured to be able to be coupled to a vent piping or vent system located without the pressure vessel, in order to vent fluids and/or vapors from the pumps located within the pressure vessel 54. Additionally, each of the support columns 58, 62, 66, 72 may have an electrical connection 96 extending therefrom. The electrical connections 96 may be coupleable to an external power source in order to provide power to the electric motors located within the pressure vessel 54.

FIGS. 4 and 5 show another embodiment of the disclosed system where one or more of the individual electric motor pump systems may be removable from the pressure vessel 54, rather than fixedly attached therein. FIG. 4 shows a cut-away view through one motor 108 pump 112 pair, wherein each of the plurality of centrifugal pumps inside the pressure vessel 54 may have a foot valve 100 installed at the suction end 104 of the pump 112. FIG. 5 shows a front view of the removable pump installed within the pressure vessel 54. While only one removable pump is shown in detail within FIG. 5, it should be understood that any number of the motor-pump pairs supported by the pressure vessel 54 may be designed to be removable. Thus, it is within the scope of this invention to have all of the pumps fixedly attached within the pressure vessel 54, all of the pumps removably inserted within the pressure vessel 54, or a subset of the pumps fixedly attached and a subset of the pumps removably inserted. As most clearly shown in FIG. 4, when the foot valve 100 is opened, fluid from the pressure vessel 54 may enter the pump 112 and pump housing 114. When the foot valve 100 is closed, fluid from the pressure vessel 54 cannot enter the pump 112 or housing 114 and can be forced to leave the pump housing 114 and return to the pressure vessel 54 by pressurizing housing 114 with inert gas. This embodiment of removable pumps, with a foot valve 100, facilitates pump replacement of a single pump without taking the multi-pump vessel out of service should a malfunction occur. The foot valve 100 may be pre-loaded with pre-load devices 130. The pre-load devices may be springs. Thus, when the weight of the motor 108 pump 112 pair is lifted up, the pre-load devices 130 will automatically close the foot valve 100. Thus, the individual pumps may be removable, and may also include separate valves at each discharge 88, as well as at each suction as described above, of the pumps for further simplifying removal of an individual pump. The valves for discharge, vent, and suction may be open when the pump is installed and closed when the pump is removed. As shown in FIG. 5, the vents 92 may include valves 115 such that two adjacent pumps 112 may be connected as shown in FIG. 2. These may be used to equalize the liquid level in each pump column and assure that the pump is fully submerged. The valve for each pump may be closed when the pump is operating or when the pump is removed.

For the embodiments shown in FIGS. 4 and 5, the time necessary to replace a single motor pump pair with a new pair is dramatically reduced from what would otherwise be required. In some cases the time savings is sufficient to such that a motor pump replacement operation may be accomplished without requiring the entire operation, of which the pump system is a part of, to be shut down. This of course is desirable and therefore beneficial to users and purchasers of such pump systems.

The disclosed pressure vessel and submerged electric motor pump system takes up a smaller footprint than a comparable number of one pump per pressure vessel systems coupled in parallel. The disclosed pressure vessel and submerged electric motor pump system requires fewer piping connections. Therefore the disclosed pressure vessel and submerged electric motor pump system should be less expensive than a comparable number of one pump per pressure vessel systems coupled in parallel, and easier to install, service and maintain.

The use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.

While the invention has been described with reference to several embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. 

1. A pressure vessel and submerged electric motor pump system comprising: a pressure vessel; at least two motor-pump assemblies located within the pressure vessel, each of the at least two motor-pump assemblies comprising: a submersible electric motor; and a submersible pump in operable communication with the submersible electrical motor, and the submersible pump is configured to pump fluid from within the pressure vessel to without the pressure vessel.
 2. The pressure vessel and submerged electric motor pump system of claim 1, wherein the pressure vessel comprises a pressure vessel pump housing for each of the motor-pump assemblies.
 3. The pressure vessel and submerged electric motor pump system of claim 1, wherein each submersible pump is in operable communication with a discharge line, and the discharge line is operably communicable with discharge piping located externally of the pressure vessel.
 4. The pressure vessel and submerged electric motor pump system of claim 1, wherein each submersible pump is in operable communication with a vent line, and the vent line is operably communicable with vent piping located externally of the pressure vessel.
 5. The pressure vessel and submerged electric motor pump system of claim 1, wherein each submersible electrical motor is in operable communication with an electrical connection, and the electrical connection is operably communicable with power source.
 6. The pressure vessel and submerged electric motor pump system of claim 1, wherein the pressure vessel has a pressure vessel vent line, and the pressure vessel vent line is operably communicable with piping located externally of the pressure vessel.
 7. The pressure vessel and submerged electric motor pump system of claim 1, wherein the pressure vessel has a drain line, and the drain line is operably communicable with piping located externally of the pressure vessel.
 8. The pressure vessel and submerged electric motor pump system of claim 1 configured such that: at least one pump is in operable communication with a discharge line via a first valve; at least one pump is in operable communication with a suction line via a second valve; at least one pump is in operable communication with a vent line via a third valve; and the at least one motor-pump assembly may be removed from the pressure vessel by closing the first, second and third valves.
 9. The pressure vessel and submerged electric motor pump system of claim 8, wherein the suction end of the at least one pump is in operable communication with a foot valve, and the foot valve is in operable communication with the pressure vessel.
 10. The pressure vessel and submerged electric motor pump system of claim 8, wherein the first valve, second valve and third valve are foot valves.
 11. The pressure vessel and submerged electric motor pump system of claim 8, further configured such that the system may operate with at least one motor-pump assembly removed from the pressure vessel.
 12. The pressure vessel and submerged electric motor pump system of claim 1, wherein a number of motor-pump assemblies located within the pressure vessel is selected between the range of three to six.
 13. The pressure vessel and submerged electric motor pump system of claim 1 wherein at least one of the at least two motor-pump assemblies is removably positionable within the pressure vessel.
 14. The pressure vessel and submerged electric motor pump system of claim 13 wherein the at least one of the at least two motor-pump assemblies includes a valve which is open when the at least one of the at least two motor-pump assemblies is installed in the pressure vessel and which closes when the at least one of the at least two motor-pump assemblies is removed from the pressure vessel.
 15. The pressure vessel and submerged electric motor pump system of claim 1 wherein the pressure vessel includes a main tank for receiving a portion of each of the at least two motor-pump assemblies and for storing a fluid, and wherein the pressure vessel further includes a support column, extending exteriorly of the main tank, for each of the at least two motor-pump assemblies.
 16. A submerged electric motor pump system comprising: a pressure vessel; a single suction and phase separation vessel in operable communication with the pressure vessel; at least two motor-pump assemblies located within the pressure vessel, each of the at least two motor-pump assemblies comprising: a submersible electric motor; and a submersible pump coupled to the submersible electrical motor, and the submersible pump is configured to pump fluid from within the pressure vessel to without the pressure vessel.
 17. The submerged electric motor pump system of claim 16 wherein the pressure vessel is configured to be in operable communication with the single suction and phase separation vessel via a single set of suction, drain and vent lines.
 18. A method for pumping a fluid from a pressure vessel, the method comprising: supplying a fluid to a pressure vessel; pumping the fluid with two or more submersible electric motor pumps located within the pressure vessel; and discharging a pumped fluid from the pressure vessel.
 19. The method of claim 18 further comprising removing one of the two or more submersible electric motor pumps from the pressure vessel.
 20. The method of claim 19 wherein supplying a fluid to a pressure vessel, pumping the fluid with two or more submersible electric motor pumps located within the pressure vessel, and discharging a pumped fluid from the pressure vessel continues during removing one of the two or more submersible electric motor pumps from the pressure vessel.
 21. A method for pumping a fluid from a pressure vessel, the method comprising: supplying power to two or more submersible electric motors located within the pressure vessel; rotating a rotor located within each of the two or more submersible electric motors; rotating two or more pump shafts each of which are within a separate pump and each of which are in operable communication with each of the rotors; pumping a fluid within the pressure vessel with each of the pumps; and discharging a pumped fluid from the pressure vessel. 